Reduction and smelting of ores



Jan. 30, 1934. BRASSERT 1,945,341

REDUCTION AND SMELIING OF ORES Filed Aug. 27, 1931 Patented Jan. 30,1934 UNITED STATES PATENT OFFICE 'Herman A. Brassert, Chicago, Ill.,assignor to H.

A. Brassert & Company, Chicago, 11]., a corporation of IllinoisApplication August 27, 1931.

'11 Claims.

This invention relates to the reduction and smelting of ores,particularly iron ores, and more particularly to the production of ametal low in carbon and at the same time the provision of a materialsaving in fuel consumption and cost.

In the usual blast furnace operation the fuel is metallurgical coke. Thecoke is charged with the ore and fiux stone in layers or more or lessintimately mixed. As a result of its size and the universallyadopted-method of feeding the charge into the furnace by means of alarge bell, the coke travels largely to the center of the furnace, thefine ore mostly remaining around the periphery next to the walls. Thisresults in a cone of coke forming in the center of the hearth extendingupward into the bosh and lower stack, particularly with the large hearthdiameter now in common use. The oxygen of the blast, in the form of O orCO2, does not reach more than a few feet into the interior. Consequentlya dead center is created in the hearth and the presence of this mass ofcoke in contact with the bath of molten iron which collects in thehearth causes the iron to saturate itself with carbon. The release ofcoke ash in the molten metal is also a detriment. Another disadvantageis the reduced production per unit of hearth area of the largerfurnaces. Another objection to the blast furnace using coke as a fuel inthe ordinary manner is that the coke although, in good practice, lessthan one half the weight of ore occupies roughly five times the volumein the furnace, which has necessitated the construction of large andhigh stacks to obtain the capacities required by modern practice.

I materially overcome these objections by my invention,-an object ofwhich is to produce a metal low in carbon direct from the ore. A further object is to reduce the size of the blast furnace for a givenoutput. It is also an object to separate and use each size of ore to itsbest advantage in the reduction and melting process It is an additionalobject to enable the use of other fuels than blast furnace coke of theusual size and quality. It is a further object to decrease radiationlosses. It is also an object to enable the use of very high blasttemperatures. Another object is to substitute reduced ore or so-calledsponge iron for coke in the center areas of the hearth. It is a furtherobject to reduce a column of ore substantially free from fines with COgas in the absence of reactive carbon. A still further object is toreduce the ore fines by direct reduction substantially removed from thecurrent of ascending gases, thus largely preventing flue Serial No.559,612

dust losses and carbon deposition on the ore. Other and further objectswill appear as the description proceeds.

In order to accomplish these objects, I have invented a new method ofblast furnace operation which consists in dividing the ore into coarseand fine, and charging them separately and charging a smaller fuel thanthe present blast furnace coke with the fines and placing them next tothe wall, whereas the coarse ore I place, preferably without fuel, inthe center of the furnace. The flux stone may be divided between the twocolumns and sized accordingly.

I have shown in the accompanying drawing one form of apparatus adaptedfor carrying out my invention.

In the drawing,

Figure 1 is a vertical section of a blast furnace; Figure 2 is afragmentary section of the top of the furnace, showing the chargingbells in a different position;

Figure 3 is a section taken on line 3-3 of Figure 1;

Figure 4 is a view similar to Figure 3, showing a modified form ofconstruction; and

Figure 5 is a view similar to Figure 3, showing a further modified form.

The blast furnace shown in Figure 1 comprises a base 11, hearth 12,tuyere coolers 13, bosh 14 and shaft section 15. The upper portion ofthe shaft is shown as flared outwardly at 16, above the normal stackline and protected by the stack line plates 17. A charge distributingtube 18 is suspended in the upper portion by the arms 19 connected tothe plates 17 at 20.

The charging hopper 21 is supported on top of the furnace and its upperend is closed by the small bell 22. The lower end of the hopper 21 isclosed by the lower bell 23 which has a periph-- eral flange 24underlying the upper edge of the distributing hopper 25. The bell 23 israised or lowered by the rod 26 while the distributing bell 25 isoperated by rods 27 which are shown connected to yoke 28. In Figure l,the positions of the bells 23 and 25, when both are lowered are shown inbroken lines. In Figure 2 the bells are shown in the relative positionswhich they assume when the bell 23 only is lowered. The fine materialadjacent the wall is shown at 29 and the core of coarse material at thecenter is shownv The furnace maybe circular in cross section as shown inFigure 3, or oval in cross section as shown in Figure 4 or it may berectangular in cross section. as shown in Figure 5.

In the use of the furnace the fine ore and the fine fuel are placedadjacent the walls of the furnace and some fine fiux material may beplaced with them. This is accomplished by placing the fine charge in thehopper 21 and then simultaneously lowering both bells 23 and 25 to thebroken line position of Figure 1. The angle of the upper face of thebells causes the fine material to flow outwardly against the furnacewall and the distributing tube 18 and the lower portion of the bell 25prevent these fines from flowing from the wall to the center.

In charging the coarser material, the hopper 21 receives the charge andthen the small bell 23 only is lowered. The coarse material then fiowsover this bell against the inside of the bell 25 which returns thematerial toward the center and into the tube 18.

By placing my fines with the preferably small sized-fuel next to thewalls, I prevent the current of gas from ascending adjacent to thewalls, forcing them up through the column of relatively coarse ore inthecenter. By coarse ore, I mean ore from which fines have been removed andof such a size that the column will be permeable to the flow of gaswithout excessive pressure. The lower the furnace the smaller the sizeof coarse ore that can and should be used, because the lower heightmeans less resistance and smaller sizes require less time for reduction,providing the column is kept permeable to the gases through the absenceof fines. By keeping the gases away from the ore fines descending nextto the wall, I keep the wall areas cool, decrease radiation and fiuedust losses and at the same time my method tends to prevent thedangerous reaction of CO in the ascending gases in presence of ironoxide, depositing molecular carbon in these fines next the wall andforming CO2, this carbon deposition having been the cause of manydestructive explosions.

The fine ore is charged mixed with the fuel, which may consist of smallsized coke, pea coke or screenings,- or it may consist, all or in part,of correspondingly sized preferably non-coking coal. In any casesufiicient fuel is charged with the fine ore to reduce it by directreduction. Additional fuel may be injected through tuyres into thehearth to furnish additional heat required for melting and/or anyadditional CO required for reducing the center column of coarser ore. Ora deficiency of carbon in the melting zone may be made up by adding cokeor other slow reacting fuel to the ore charges.

While some of the carbon charged with the ore fines will be absorbedduring the descent in reduction of ore, the balance will arrive in frontof thetuyres, preheated by radiation and convection from thehotter-interior of the furnace. I employ a highly heated blast,preferably above 1600 F. which accelerates combustion and combined withthe higher reactivity and the relatively large carbon surfaces offeredby the smaller fuel charged, as compared to blast furnace coke, which isboth hard and large, shortens and intensifies the zone of combustion,producing also a maximum of CO gas within a given zone. The heat thuscreated will rapidly melt the reduced and highly preheated oresdescending'in the center. There being no carbon masses in the center,the melted iron will remain low. in carbon. If a small carbon content isdesired in order to obtain desirable fluidity of the metal, the same maybe derived from additional fuel charged at the top or admitted throughthe tuyeres. If on the other hand a very low carbon melt is desired theratio of the fuel charged at the top to the total fuel is decreased,additional heat or fuel being supplied through tuyeres.

To carry out my invention I can use the ordinary blast furnace now incommon use, or I may use the type of furnace described in co-pendingapplications, Ser. No. 549,722 filed July 8, 1931 and Ser. No.553,250filed July 27, 1931, particularly if a considerable proportion offuel injected at the bottom is used. Or I may use a furnace of oval orrectangular shape, as shown in Figures 4 and 5 in which case there isthe advantage of carrying the heat of combustion further in toward thecenter. It has been found that with the use of small fuel and highlypreheated blast that the zone of combustion becomes very limited inextent and the highest temperatures will not prevail beyondapproximately 12 inches from the tuyeres. It is therefore desirable toreduce the 95 distance between opposing tuyeres in order to obtain ashigh a temperature as possible in the center of the hearth where themelting of the iron sponge takes place. In a furnace having a circularcross section this can only be accom-' plished by decreasing the hearthdiameter which in turn involves a bosh with a flat angle. This isobjectionable owing to the tendency of the fine materials to hang up onthe ,bosh walls. If the furnace is rectangular or oval opposing tuyeresmay be brought closer together without requiring a fiat bosh or any boshat all. In any case my furnace for the same rate of output will not benearly as large as the present blast furnace. I

Various changes may be made in-carrying out my invention, as for examplesome iron or steel scrap may be added to the ore as is done in blastfurnace practice in order to increase the output or melt up cheapmaterials of that character which may be available.

The furnaces shown in the accompanying drawing and the method ofoperation described are to be understood as illustrative only as themethod may be carried out in other furnaces and the method may be variedto meet different conditions and requirements and I contemplate suchchanges and modifications as come within the spirit and scope of theappended claims.

I claim: v

1. The method of producing a metal of low carbon content from iron oresin a single-shaft furnace operation which comprises reducing the coarserportion of the ores with carbon monoxide gas produced in the hearth andbosh of the fur- 3 mace and the finer portion by direct reduction withcarbon monoxide formed in direct contact with the ore from solid carboncharged with the ore.

2. The method of producing a metal'of low carbon content from iron oresin a single shaft furnace operation which comprises reducing the coarserportion of the ores with carbon monoxide gas produced in the hearth andbosh of the furnace and the finer portion by direct reduction with solidcarbon charged with the ore and melting the two portions together.

3. The method of producing a metal of carbon content below two per centfrom iron ores in a single shaft furnace operation which comprisesreducing the coarser portion of the ores with carbon monoxide gasproduced in the hearth and bosh of the furnace and the finer portion bydirect reduction with carbon monoxide formed .in 1

direct contact with the ore from solid carbon charged with the ore.

4. The method of producing in a shaft furnace a metal low in carbon fromiron ores which comprises separating the ore into coarser and finer oreportions, thereafter separately charging small fuel mixed with the finerportion of the ore into the vertically extending portion of 1 thefurnace adjacent the walls, charging the coarser ore substantially freeof fuel into the vertically extending central portion of the furnace,and reducing and smelting both coarse and fine ores in a single furnaceoperation.

5. The method of producing in a shaft furnace a metal low in carbon fromiron ores which comprises separating the ore into coarser and finer oreportions, thereafter separately charging small coal mixed with the finerportion of the ore into the vertically extending portion of the furnaceadjacent the walls, charging the coarser ore substantially free of fuelinto the vertically extending central portion of the furnace, andreducing and smelting both coarse and fine ores in a single furnaceoperation.

6. The method of producing in a shaft furnace a metal low in carbon fromiron ores which comprises separating the ore into coarser and finer oreportions, thereafter separately charging coke braize mixed with thefiner portion of the ore into the vertically extending portion of thefurnace adjacent the walls, charging the coarser ore substantially freeof fuel into the vertically extending central portion of the furnace,and reducing and smelting both coarse and fine ores in a single furnaceoperation.

7. The method of charging a blast furnace which comprises placing orefines and fuel adjacent the furnace wall and placing the coarser oresubstantially free of fuel in the center ofthe furnace.

8. The method of charging a blast furnace which comprises firstseparating the coarser ores causing them to descend through said sectionin.

countercurrent movement to the gases ascending in said section, andreducing and smelting the ores in the furnace.

10. The method of producing a low carbon melt of iron in a shaft furnacewhich comprises charging coarser ores in one vertically extending por-=tion of the furnace, collecting such coarser portion of the reduced andmelting ores in one portion of a furnace hearth in the absence ofsubstantial amounts of carbon, bringing the balance of the ores downmixed with carbon in another vertically extending portion of the furnaceand simultaneously reducing and smelting both the coarse and fine ores.

11. The method of producing a low carbon melt of iron in a shaft furnacehaving tuyres which comprisesv charging the coarser portion of the oresin the vertically extending central portion of the furnace, collectingsuch portion of the reduced and melting ores in the center of a furnacehearth in the absence of substantial amounts of carbon, charging thebalance of the ores mixed with carbon around the periphery of thefurnace and bringing them down at the periphery of the hearth and infront of the tuyres, and simultaneously reducing and smelting both thecoarse and fine ores.

HERMAN A. BRASSERT.

